Systems and methods for welding electrodes

ABSTRACT

The invention relates generally to welding and, more specifically, to welding wires for arc welding, such as Gas Metal Arc Welding (GMAW) or Flux Core Arc Welding (FCAW). In one embodiment, a tubular welding wire includes a sheath and a core, and the core includes an organic stabilizer component. Further, the organic stabilizer component includes an organic sub-component configured to release hydrogen near a surface of a workpiece during welding, and includes a Group I metal, Group II metal, or a combination thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part application of U.S.application Ser. No. 13/596,713, entitled “SYSTEMS AND METHODS FORWELDING ELECTRODES,” filed on Aug. 28, 2012, the disclosure of which ishereby incorporated by reference in its entirety for all purposes.

BACKGROUND

The invention relates generally to welding and, more specifically, toelectrodes for arc welding, such as Gas Metal Arc Welding (GMAW) or FluxCore Arc Welding (FCAW).

Welding is a process that has become ubiquitous in various industriesfor a variety of applications. For example, welding is often used inapplications such as shipbuilding, offshore platform, construction, pipemills, and so forth. Certain welding techniques (e.g., Gas Metal ArcWelding (GMAW), Gas-shielded Flux Core Arc Welding (FCAW-G), and GasTungsten Arc Welding (GTAW)), typically employ a shielding gas (e.g.,argon, carbon dioxide, or oxygen) to provide a particular localatmosphere in and around the welding arc and the weld pool during thewelding process, while others (e.g., Flux Core Arc Welding (FCAW),Submerged Arc Welding (SAW), and Shielded Metal Arc Welding (SMAW)) donot. Additionally, certain types of welding may involve a weldingelectrode in the form of welding wire. Welding wire may generallyprovide a supply of filler metal for the weld as well as provide a pathfor the current during the welding process. Furthermore, certain typesof welding wire (e.g., tubular welding wire) may include one or morecomponents (e.g., flux, arc stabilizers, or other additives) that maygenerally alter the welding process and/or the properties of theresulting weld.

BRIEF DESCRIPTION

In one embodiment, a tubular welding wire includes a sheath and a core,and the core includes an organic stabilizer component. Further, theorganic stabilizer component includes an organic sub-componentconfigured to release hydrogen near a surface of a workpiece duringwelding, and includes a Group I metal, Group II metal, or a combinationthereof

In another embodiment, a tubular welding wire includes a sheath and acore. Further, the core includes a rare earth silicide component, andwherein the rare earth silicide comprises cerium, lanthanum, or acombination thereof

In another embodiment, a tubular welding wire configured to weld coatedmetal workpieces and to provide a weld having a porosity less thanapproximately 0.25 inches per inch of the weld at travel speeds greaterthan approximately 30 inches per minute.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a block diagram of a gas metal arc welding (GMAW) system, inaccordance with embodiments of the present disclosure;

FIG. 2 is a cross-sectional view of a tubular welding wire, inaccordance with embodiments of the present disclosure;

FIG. 3 is a process by which the tubular welding wire may be used toweld a workpiece, in accordance with embodiments of the presentdisclosure; and

FIG. 4 is a process for manufacturing the tubular welding wire, inaccordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements. Itshould be appreciated that, as used herein, the term “tubular weldingelectrode” or “tubular welding wire” may refer to any welding wire orelectrode having a metal sheath and a granular or powdered core, such asmetal-cored or flux-cored welding electrodes. It should also beappreciated that the term “stabilizer” or “additive” may be generallyused to refer to any component of the tubular welding that improves thequality of the arc, the quality of the weld, or otherwise affect thewelding process. Furthermore, as used herein, “approximately” maygenerally refer to an approximate value that may, in certainembodiments, represent a difference (e.g., higher or lower) of less than0.01%, less than 0.1%, or less than 1% from the actual value. That is,an “approximate” value may, in certain embodiments, be accurate towithin (e.g., plus or minus) 0.01%, within 0.1%, or within 1% of thestated value.

As mentioned, certain types of welding electrodes (e.g., tubular weldingwire) may include one or more components (e.g., flux, arc stabilizers,or other additives) that may generally alter the welding process and theproperties of the resulting weld. For example, certain presentlydisclosed welding electrode embodiments include an organic stabilizer(e.g., a derivatized cellulose-based component) that may generallyimprove the stability of the arc while providing a reducing atmosphereconducive to welding coated workpieces (e.g., galvanized workpieces).Certain presently disclosed welding electrode embodiments also include arare earth silicide component that may generally help to control theshape and penetration of the arc during welding. Furthermore, thedisclosed welding electrode embodiments may include other componentssuch as, for example, a carbon component (e.g., graphite, carbon black,or other suitable carbon component), and an agglomerated stabilizercomponent (e.g., a potassium/titanate/manganate agglomerate), as setforth in detail below.

Accordingly, the presently disclosed welding electrodes enhance theweldability of coated (e.g., galvanized, galvannealed, painted, and soforth) workpieces and/or thinner (e.g., 20-, 22-, 24-gauge, or thinner)workpieces, even at high travel speed (e.g., greater than 40 in/min).Additionally, the disclosed welding electrodes generally enableacceptable welds under different welding configurations (e.g., directcurrent electrode negative (DCEN), direct current electrode positive(DCEP), alternating currents (AC), and so forth) and/or differentwelding methods (e.g., involving circular or serpentine weldingelectrode movements during welding). Additionally, certain presentlydisclosed welding electrodes may be drawn to particular diameters (e.g.,0.030 in, 0.035 in, 0.040 in, or other suitable diameters) to providegood heat transfer and deposition rates.

Turning to the figures, FIG. 1 illustrates an embodiment of a gas metalarc welding (GMAW) system 10 that utilizes a welding electrode (e.g.,tubular welding wire) in accordance with the present disclosure. Itshould be appreciated that, while the present discussion may focusspecifically on the GMAW system 10 illustrated in FIG. 1, the presentlydisclosed welding electrodes may benefit any arc welding process (e.g.,FCAW, FCAW-G, GTAW, SAW, SMAW, or similar arc welding process) that usesa welding electrode. The welding system 10 includes a welding powersource 12, a welding wire feeder 14, a gas supply system 16, and awelding torch 18. The welding power source 12 generally supplies powerto the welding system 10 and may be coupled to the welding wire feeder14 via a cable bundle 20 as well as coupled to a workpiece 22 using alead cable 24 having a clamp 26. In the illustrated embodiment, thewelding wire feeder 14 is coupled to the welding torch 18 via a cablebundle 28 in order to supply consumable, tubular welding wire (i.e., thewelding electrode) and power to the welding torch 18 during operation ofthe welding system 10. In another embodiment, the welding power unit 12may couple and directly supply power to the welding torch 18.

The welding power source 12 may generally include power conversioncircuitry that receives input power from an alternating current powersource 30 (e.g., an AC power grid, an engine/generator set, or acombination thereof), conditions the input power, and provides DC or ACoutput power via the cable 20. As such, the welding power source 12 maypower the welding wire feeder 14 that, in turn, powers the welding torch18, in accordance with demands of the welding system 10. The lead cable24 terminating in the clamp 26 couples the welding power source 12 tothe workpiece 22 to close the circuit between the welding power source12, the workpiece 22, and the welding torch 18. The welding power source12 may include circuit elements (e.g., transformers, rectifiers,switches, and so forth) capable of converting the AC input power to adirect current electrode positive (DCEP) output, direct currentelectrode negative (DCEN) output, DC variable polarity, pulsed DC, or avariable balance (e.g., balanced or unbalanced) AC output, as dictatedby the demands of the welding system 10. It should be appreciated thatthe presently disclosed welding electrodes (e.g., tubular welding wire)may enable improvements to the welding process (e.g., improved arcstability and/or improved weld quality) for a number of different powerconfigurations.

The illustrated welding system 10 includes a gas supply system 16 thatsupplies a shielding gas or shielding gas mixtures from one or moreshielding gas sources 17 to the welding torch 18. In the depictedembodiment, the gas supply system 16 is directly coupled to the weldingtorch 18 via a gas conduit 32. In another embodiment, the gas supplysystem 16 may instead be coupled to the wire feeder 14, and the wirefeeder 14 may regulate the flow of gas from the gas supply system 16 tothe welding torch 18. A shielding gas, as used herein, may refer to anygas or mixture of gases that may be provided to the arc and/or weld poolin order to provide a particular local atmosphere (e.g., to shield thearc, improve arc stability, limit the formation of metal oxides, improvewetting of the metal surfaces, alter the chemistry of the weld deposit,and so forth). In certain embodiments, the shielding gas flow may be ashielding gas or shielding gas mixture (e.g., argon (Ar), helium (He),carbon dioxide (CO₂), oxygen (O₂), nitrogen (N₂), similar suitableshielding gases, or any mixtures thereof). For example, a shielding gasflow (e.g., delivered via the conduit 32) may include Ar, Ar/CO₂mixtures, Ar/CO₂/O₂ mixtures, Ar/He mixtures, and so forth. By specificexample, in certain embodiments, the shielding gas flow may include 90%Ar and 10% CO₂.

Accordingly, the illustrated welding torch 18 generally receives thewelding electrode (i.e., the tubular welding wire), power from thewelding wire feeder 14, and a shielding gas flow from the gas supplysystem 16 in order to perform GMAW of the workpiece 22. Duringoperation, the welding torch 18 may be brought near the workpiece 22 sothat an arc 34 may be formed between the consumable welding electrode(i.e., the welding wire exiting a contact tip of the welding torch 18)and the workpiece 22. Additionally, as discussed below, by controllingthe composition of the welding electrode (i.e., the tubular weldingwire), the chemistry of the arc 34 and/or the resulting weld (e.g.,composition and physical characteristics) may be varied. For example,the welding electrode may include fluxing or alloying components thatmay affect the welding process (e.g., act as arc stabilizers) and,further, may become at least partially incorporated into the weld,affecting the mechanical properties of the weld. Furthermore, certaincomponents of the welding electrode (i.e., welding wire) may alsoprovide additional shielding atmosphere near the arc, affect thetransfer properties of the arc 34, deoxidize the surface of theworkpiece, and so forth.

A cross-section of an embodiment of the presently disclosed welding wireis illustrated in FIG. 2. FIG. 2 illustrates a tubular welding wire 50that includes a metallic sheath 52, which encapsulates a granular orpowdered core 54 (also referred to as filler). In certain embodiments,the tubular welding wire 50 may comply with one or more American WeldingSociety (AWS) standards. For example, in certain embodiments, thetubular welding wire 50 may be in accordance with AWS A5.18(“SPECIFICATION FOR CARBON STEEL ELECTRODES AND RODS FOR GAS SHEILDEDARC WELDING”) and/or with AWS A5.36 (“SPECIFICATION FOR CARBON ANDLOW-ALLOY STEEL FLUX CORED ELECTRODES FOR FLUX CORED ARC WELDING ANDMETAL CORED ELECTRODES FOR GAS METAL ARC WELDING”).

The metallic sheath 52 of the tubular welding wire 50 illustrated inFIG. 2 may be manufactured from any suitable metal or alloy, such assteel. It should be appreciated that the composition of the metallicsheath 52 may affect the composition of the resulting weld and/or theproperties of the arc 34. In certain embodiments, the metallic sheath 52may account for between approximately 80% and 90% of the total weight ofthe tubular welding wire 50. For example, in certain embodiments, themetallic sheath 52 may provide approximately 84% or approximately 86% ofthe total weight of the tubular welding wire 50.

As such, the metallic sheath 52 may include certain additives orimpurities (e.g., alloying components, carbon, alkali metals, manganese,or similar compounds or elements) that may be selected to providedesired weld properties. In certain embodiments, the metallic sheath 52of the tubular welding wire 50 may be a low-carbon strip that includes arelatively small (e.g., lower or reduced) amount of carbon (e.g., lessthan approximately 0.06%, less than approximately 0.07%, or less thanapproximately 0.08% carbon by weight). For example, in an embodiment,the metallic sheath 52 of the tubular welding wire 50 may includebetween approximately 0.07% and 0.08% carbon by weight. Additionally, incertain embodiments, the metallic sheath 52 may be made of steelgenerally having a small number of inclusions. For example, in certainembodiments, the metallic sheath 52 may include between approximately0.25% and approximately 0.5%, or approximately 0.34% manganese byweight. By further example, in certain embodiments, the metallic sheath52 may include less than approximately 0.02% phosphorus or sulfur byweight. The metallic sheath 52, in certain embodiments, may also includeless than approximately 0.04% silicon by weight, less than approximately0.05% aluminum by weight, less than approximately 0.1% copper by weight,and/or less than approximately 0.02% tin by weight.

The granular core 54 of the illustrated tubular welding wire 50 maygenerally be a compacted powder. In certain embodiments, the granularcore 54 may account for between approximately 7% and approximately 40%,or between approximately 10% and approximately 20%, of the total weightof the tubular welding wire 50. For example, in certain embodiments, thegranular core 54 may provide approximately 14%, approximately 15%, orapproximately 16% of the total weight of the tubular welding wire 50.Furthermore, in certain embodiments, the components of the granular core54, discussed below, may be homogenously or non-homogenously (e.g., inclumps or clusters 56) disposed within the granular core 54. Forexample, the granular core 54 of certain welding electrode embodiments(e.g., metal-cored welding electrodes) may include one or more metals(e.g., iron, iron titanium, iron silicon, or other alloys or metals)that may provide at least a portion of the filler metal for the weld. Byspecific example, in certain embodiments, the granular core 54 mayinclude between approximately 70% and approximately 75% iron powder, aswell as other alloying components, such as ferro-titanium (e.g., 40%grade), ferro-magnesium-silicon, and ferro-silicon powder (e.g., 50%grade, unstabilized). Other examples of components that may be presentwithin the tubular welding wire 50 (i.e., in addition to the one or morecarbon sources and the one or more alkali metal and/or alkali earthmetal compounds) include other stabilizing, fluxing, and alloyingcomponents, such as may be found in METALLOY X-CEL™ welding electrodesavailable from Illinois Tool Works, Inc.

Additionally, presently disclosed embodiments of the tubular weldingwire 50 may include an organic stabilizer disposed in the granular core54. The organic stabilizer may be any organic molecule that includes oneor more alkali metal ions (e.g., Group I: lithium (Li), sodium (Na),potassium (K), rubidium (Rb), cesium (Cs)) or alkali earth metal ions(e.g., Group II: beryllium (Be), magnesium (Mg), calcium (Ca), strontium(Sr), or barium (Ba)). That is, in certain embodiments, the organicstabilizer includes an organic subcomponent (e.g., an organic moleculeor polymer), which includes carbon, hydrogen, and oxygen, and may bechemically (e.g., covalently or ionically) bonded to the alkali metal oralkali earth metal ions. In other embodiments, the organic stabilizermay include an organic sub-component (e.g., an organic molecule orpolymer, such as cellulose) that has been mixed with (e.g., notchemically bonded with) the alkali metal and/or alkali earth metal salt(e.g., potassium oxide, potassium sulfate, sodium oxide, etc.).

By specific example, in certain embodiments, the organic stabilizer maybe a cellulose-based (e.g., cellulosic) component including a cellulosechain that has been derivatized to form a sodium or potassium salt(e.g., sodium or potassium carboxymethyl cellulose). For example, incertain embodiments, the cellulose-based organic stabilizer may besodium carboxymethyl cellulose having a degree of substitution (DS)ranging from approximately 0.5 and approximately 2.5. In general, the DSof a derivatized cellulose may be a real number between 0 and 3.representing an average number of substituted hydroxyl moieties in eachmonomer unit of the polysaccharide. In other embodiments, the organicstabilizer may be other organic molecules that include one or more GroupI/Group II ions. For example, in certain embodiments, the organicstabilizer may include derivatized sugars (e.g., derivatized sucrose,glucose, etc.) or polysaccharides having one or more carboxylic acids orsulfate moieties available to form an alkali metal or alkali earth metalsalt. In other embodiments, the organic stabilizer may include soap-likemolecules (e.g., sodium dodecyl sulfate or sodium stearate) oralginates. Additionally, in certain embodiments, the organic stabilizermay account for less than approximately 10%, between approximately 0.05%and approximately 5%, between approximately 0.1% and approximately 3%,between approximately 0.25% and approximately 2.5%, betweenapproximately 0.5% and approximately 1.5%, or approximately 1% of thegranular core 54 by weight. Additionally, in certain embodiments, theorganic stabilizer may account for less than approximately 5%, betweenapproximately 0.05% and approximately 3%, between approximately 0.08%and approximately 2%, between approximately 0.1% and approximately 1%,or approximately 0.15% of the tubular welding wire 50 by weight.

It may be appreciated that the organic stabilizer component of thetubular welding wire 50 may be maintained at a suitable level such thata reducing environment (e.g., hydrogen-rich) may be provided near thewelding arc, but without introducing substantial porosity into the weld.It should further be appreciated that utilizing an organic molecule as adelivery vehicle for at least a portion of the Group I/Group II ions tothe welding arc, as presently disclosed, may not be widely used sinceorganic molecules may generate hydrogen under the conditions of the arc,which may result in porous and/or weak welds for mild steels. However,as set forth below, using the presently disclosed organic stabilizersafford quality welds (e.g., low-porosity welds), even when welding athigh travel speed on coated (e.g., galvanized) and/or thin workpieces.

Additionally, presently disclosed embodiments of the tubular weldingwire 50 may also include a carbon component disposed in the granularcore 54. For example, the carbon source present in the granular core 54and/or the metal sheath 52 may be in a number of forms and may stabilizethe arc 34 and/or increase the carbon content of the weld. For example,in certain embodiments, graphite, graphene, nanotubes, fullerenes and/orsimilar substantially sp²-hybridized carbon sources may be utilized asthe carbon source in the tubular welding wire 50. Furthermore, incertain embodiments, graphene or graphite may be used to also provideother components (e.g., moisture, gases, metals, and so forth) that maybe present in the interstitial space between the sheets of carbon. Inother embodiments, substantially sp³-hybridized carbon sources (e.g.,micro- or nano-diamond, carbon nanotubes, buckyballs) may be used as thecarbon source. In still other embodiments, substantially amorphouscarbon (e.g., carbon black, lamp black, soot, and/or similar amorphouscarbon sources) may be used as the carbon source. Furthermore, while thepresent disclosure may refer to this component as a “carbon source,” itshould be appreciated that the carbon source may be a chemicallymodified carbon source that may contain elements other than carbon(e.g., oxygen, halogens, metals, and so forth). For example, in certainembodiments, the tubular welding wire 50 may include a carbon blackcomponent in the granular core 54 that may contain a manganese contentof approximately 20%. In certain embodiments, the carbon component ofthe tubular welding wire 50 may be powdered or granular graphite.Additionally, in certain embodiments, the carbon component may accountfor less than approximately 10%, between approximately 0.01% andapproximately 5%, between approximately 0.05% and approximately 2.5%,between approximately 0.1% and approximately 1%, or approximately 0.5%of the granular core 54 by weight. In certain embodiments, the carboncomponent may account for less than approximately 5%, betweenapproximately 0.01% and approximately 2.5%, between approximately 0.05%and approximately 0.1%, or approximately 0.08% of the tubular weldingwire 50 by weight.

Furthermore, in addition to the organic stabilizer discussed above, thetubular welding wire 50 may also include one or more inorganicstabilizers to further stabilize the arc 34. That is, the granular core54 of the tubular welding wire 50 may include one or more compounds ofthe Group 1 and Group 2 elements (e.g., Li, Na, K, Rb, Cs, Be, Mg, Ca,Sr, Ba). A non-limiting list of example compounds include: Group 1(i.e., alkali metal) and Group 2 (i.e., alkaline earth metal) silicates,titanates, carbonates, halides, phosphates, sulfides, hydroxides,oxides, permanganates, silicohalides, feldspars, pollucites,molybdenites, and molybdates. For example, in an embodiment, thegranular core 54 of the tubular welding wire 50 may include potassiummanganese titanate, potassium sulfate, sodium feldspar, potassiumfeldspar, and/or lithium carbonate. By specific example, the granularcore 54 may include potassium silicate, potassium titanate, potassiumalginate, potassium carbonate, potassium fluoride, potassium phosphate,potassium sulfide, potassium hydroxide, potassium oxide, potassiumpermanganate, potassium silicofluoride, potassium feldspar, potassiummolybdates, or a combination thereof as the potassium source. Similarexamples of stabilizing compounds that may be used are described in U.S.Pat. No. 7,087,860, entitled “STRAIGHT POLARITY METAL CORED WIRES,” andU.S. Pat. No. 6,723,954, entitled “STRAIGHT POLARITY METAL CORED WIRE,”which are both incorporated by reference in their entireties for allpurposes.

Furthermore, for certain embodiments of the presently disclosed tubularwelding wire 50, one or more inorganic stabilizers may be included inthe granular core 54 in the form of an agglomerate or frit. That is,certain embodiments of the tubular welding wire 50 may include one ormore of the inorganic stabilizers described above in an agglomerate orfrit that may stabilize the arc during welding. The term “agglomerate”or “frit,” as used herein, refers to a mixture of compounds that havebeen fired or heated in a calciner or oven such that the components ofthe mixture are in intimate contact with one another. It should beappreciated that the agglomerate may have subtly or substantiallydifferent chemical and/or physical properties than the individualcomponents of the mixture used to form the agglomerate. For example,agglomerating, as presently disclosed, may provide a frit that is bettersuited for the weld environment than the non-agglomerated materials.

In certain embodiments, the granular core 54 of the tubular welding wire50 may include an agglomerate of one or more alkali metal or alkalineearth metal compounds (e.g., potassium oxide, sodium oxide, calciumoxide, magnesium oxide, or other suitable alkali metal or alkaline earthmetal compound). In other embodiments, the granular core 54 of thetubular welding wire 50 may include an agglomerate of a mixture ofalkali metal or alkaline earth metal compound and other oxides (e.g.,silicon dioxide, titanium dioxide, manganese dioxide, or other suitablemetal oxides). For example, one embodiment of a tubular welding wire 50may include an agglomerated potassium source including of a mixture ofpotassium oxide, silica, and titania. By further example, anotherembodiment of a tubular welding wire 50 may include in the granular core54 another stabilizing agglomerate having a mixture of potassium oxide(e.g., between approximately 22% and 25% by weight), silicon oxide(e.g., between approximately 10% and 18% by weight), titanium dioxide(e.g., between approximately 38% and 42% by weight), and manganese oxideor manganese dioxide (e.g., between approximately 16% and 22% byweight). In certain embodiments, an agglomerate may include betweenapproximately 5% and 75% alkali metal and/or alkaline earth metalcompound (e.g., potassium oxide, calcium oxide, magnesium oxide, orother suitable alkali metal and/or alkaline earth metal compound) byweight, or between approximately 5% and 95% alkali metal and/or alkalineearth metal (e.g., potassium, sodium, calcium, magnesium, or othersuitable alkali metal and/or alkaline earth metal) by weight.Furthermore, in certain embodiments, other chemical and/or physicalfactors (e.g., maximizing alkali metal and/or alkaline earth metalloading, acidity, stability, and/or hygroscopicity of the agglomerate)may be considered when selecting the relative amounts of each componentpresent in the agglomerate mixture. Additionally, in certainembodiments, the agglomerate may account for less than approximately10%, between approximately 0.1% and approximately 6%, betweenapproximately 0.25% and approximately 2.5%, between approximately 0.5%and approximately 1.5%, or approximately 1% of the granular core 54 byweight. In certain embodiments, the agglomerate may account for lessthan approximately 5%, between approximately 0.05% and approximately2.5%, between approximately 0.1% and approximately 0.5%, orapproximately 0.15% of the tubular welding wire 50 by weight.

Additionally, the granular core 54 of the tubular welding wire 50 mayalso include other components to control the welding process. Forexample, rare earth elements may generally affect the stability and heattransfer characteristics of the arc 34. As such, in certain embodiments,the tubular welding wire 50 may include a rare earth component, such asthe Rare Earth Silicide (e.g., available from Miller and Company ofRosemont, Ill.), which may include rare earth elements (e.g., cerium andlanthanum) and other non-rare earth elements (e.g., iron and silicon).In other embodiments, any material including cerium or lanthanum (e.g.,nickel lanthanum alloys) may be used in an amount that does not spoilthe effect of the present approach. By specific example, in certainembodiments, the rare earth component may account for less thanapproximately 10%, between approximately 0.01% and approximately 8%,between approximately 0.5% and approximately 5%, between approximately0.25% and approximately 4%, between approximately 1% and approximately3%, between approximately 0.75% and approximately 2.5%, or approximately2% of the granular core 54 by weight. In certain embodiments, the rareearth component may account for less than approximately 5%, betweenapproximately 0.01% and approximately 2.5%, between approximately 0.1%and approximately 0.75%, or approximately 0.3% of the tubular weldingwire 50 by weight.

Furthermore, the tubular welding wire 50 may, additionally oralternatively, include other elements and/or minerals to provide arcstability and to control the chemistry of the resulting weld. Forexample, in certain embodiments, the granular core 54 and/or themetallic sheath 52 of the tubular welding wire 50 may include certainelements (e.g., titanium, manganese, zirconium, fluorine, or otherelements) and/or minerals (e.g., pyrite, magnetite, and so forth). Byspecific example, certain embodiments may include zirconium silicide,nickel zirconium, or alloys of titanium, aluminum, and/or zirconium inthe granular core 54. In particular, sulfur containing compounds,including various sulfide, sulfate, and/or sulfite compounds (e.g., suchas molybdenum disulfide, iron sulfide, manganese sulfite, bariumsulfate, calcium sulfate, or potassium sulfate) or sulfur-containingcompounds or minerals (e.g., pyrite, gypsum, or similarsulfur-containing species) may be included in the granular core 54 toimprove the quality of the resulting weld by improving bead shape andfacilitating slag detachment, which may be especially useful whenwelding galvanized workpieces, as discussed below. Furthermore, incertain embodiments, the granular core 54 of the tubular welding wire 50may include multiple sulfur sources (e.g., manganese sulfite, bariumsulfate, and pyrite), while other embodiments of the tubular weldingwire 50 may include only a single sulfur source (e.g., potassiumsulfate) without including a substantial amount of another sulfur source(e.g., pyrite or iron sulfide). For example, in an embodiment, thegranular core 54 of the tubular welding wire 50 may include betweenapproximately 0.01% and approximately 0.5%, or approximately 0.2%potassium sulfate.

Generally speaking, the tubular welding wire 50 may generally stabilizethe formation of the arc 34 to the workpiece 22. As such, the disclosedtubular welding wire 50 may improve more than one aspect of the weldingprocess (e.g., deposition rate, travel speed, splatter, bead shape, weldquality, etc.). It should further be appreciated that the improvedstability of the arc 34 may generally enable and improve the welding ofcoated metal workpieces and thinner workpieces. For example, in certainembodiments, the coated metal workpieces may include galvanized,galvanealed (e.g., a combination of galvanization and annealing), orsimilar zinc-coated workpieces. A non-limiting list of example coatedworkpieces further includes dipped, plated (e.g., nickel-plated,copper-plated, tin-plated, or electroplated or chemically plated using asimilar metal), chromed, nitrite-coated, aluminized, or carburizedworkpieces. For example, in the case of galvanized workpieces, thepresently disclosed tubular welding wire 50 may generally improve thestability and control the penetration of the arc 34 such that a goodweld may be achieved despite the zinc coating on the outside of theworkpiece 22. Additionally, by improving the stability of the arc 34,the disclosed tubular welding wire 50 may generally enable the weldingof thinner workpieces than may be possible using other weldingelectrodes. For example, in certain embodiments, the disclosed tubularwelding wire 50 may be used to weld metal having an approximately 14-,16-, 18-, 20-, 22-, 24-gauge, or even thinner workpieces. For example,in certain embodiments, the disclosed tubular welding wire 50 may enablewelding workpieces having a thickness less than approximately 5 mm, lessthan 3 mm, or even less than approximately 1.5 mm.

Furthermore, the presently disclosed tubular welding wire 50 enableswelding (e.g., welding of thin gauge galvanized steels) at travel speedsin excess of 30 or even 40 inches per minute. For example, the tubularwelding wire 50 readily enables high quality fillet welds at travelspeeds above 40 inches per minute (e.g., 35 or 45 inches per minute)with low weld porosity. That is, the presently disclosed tubular weldingwire 50 may enable higher (e.g., 50% to 75% higher) travel speeds thanother solid-cored, metal-cored, or flux-cored welding wires. It shouldbe appreciated that higher travel speeds may enable higher productionrates (e.g., on a production line) and reduce costs. Additionally, thepresently disclosed tubular welding wire 50 exhibits good gap handlingand provides excellent weld properties (e.g., strength, ductility,appearance, and so forth) using a wide operating process window.Further, the tubular welding wire 50 generally produces less smoke andspatter than other solid-cored, metal-cored, or flux-cored weldingwires.

Furthermore, the disclosed tubular welding wire 50 may also be combinedwith certain welding methods or techniques (e.g., techniques in whichthe welding electrode moves in a particular manner during the weldoperation) that may further increase the robustness of the weldingsystem 10 for particular types of workpieces. For example, in certainembodiments, the welding torch 18 may be configured to cyclically orperiodically move the electrode in a desired pattern (e.g., a circular,spin arc, or serpentine pattern) within the welding torch 18 in order tomaintain an arc 34 between the tubular welding wire 50 and the workpiece22 (e.g., only between the sheath 52 of the tubular welding wire 50 andthe workpiece 22). By specific example, in certain embodiments, thedisclosed tubular welding wire 50 may be utilized with welding methodssuch as those described in U.S. Provisional Patent Application Ser. No.61/576,850, entitled “DC ELECTRODE NEGATIVE ROTATING ARC WELDING METHODAND SYSTEM,”; in U.S. patent application Ser. No. 13/681,687, entitled“DC ELECTRODE NEGATIVE ROTATING ARC WELDING METHOD AND SYSTEM”; and inU.S. Provisional Patent Application Ser. No. 61/676,563, entitled“ADAPTABLE ROTATING ARC WELDING METHOD AND SYSTEM”; which are allincorporated by reference herein in their entireties for all purposes.It should be appreciated that such welding techniques may be especiallyuseful when welding thin workpieces (e.g., having 20-, 22-, or 24-gaugethickness), as mentioned above.

FIG. 3 illustrates an embodiment of a process 60 by which a workpiece 22may be welded using the disclosed welding system 10 and tubular weldingwire 50. The illustrated process 60 begins with feeding (block 62) thetubular welding electrode 50 (i.e., the tubular welding wire 50) to awelding apparatus (e.g., welding torch 18). As set forth above, incertain embodiments, the tubular welding wire 50 may include one or moreorganic stabilizer components (e.g., sodium carboxymethyl cellulose),one or more carbon components (e.g., graphite powder), and one or morerare earth components (e.g., rare earth silicide). Further, the tubularwelding wire 50 may have an outer diameter between approximately 0.024in and approximately 0.062 in, between approximately 0.030 in andapproximately 0.060 in, between 0.035 in and approximately 0.052 in, orapproximately 0.040 in. It may also be appreciated that, in certainembodiments, the welding system 10 may feed the tubular welding wire 50at a suitable rate to enable a travel speed greater than 30 in/min orgreater than 40 in/min.

Additionally, the process 60 includes providing (block 64) a shieldinggas flow (e.g., 100% argon, 100% carbon dioxide, 75% argon/25% carbondioxide, 90% argon/10% carbon dioxide, or similar shielding gas flow)near the contact tip of the welding apparatus (e.g., the contact tip ofthe torch 18). In other embodiments, welding systems may be used that donot use a gas supply system (e.g., such as the gas supply system 16illustrated in FIG. 1) and one or more components (e.g., potassiumcarbonate) of the tubular welding wire 50 may decompose to provide ashielding gas component (e.g., carbon dioxide).

Next, the tubular welding wire 50 may be brought near (block 66) theworkpiece 22 to strike and sustain an arc 34 between the tubular weldingwire 50 and the workpiece 22. It should be appreciated that the arc 34may be produced using, for example, a DCEP, DCEN, DC variable polarity,pulsed DC, balanced or unbalanced AC power configuration for the GMAWsystem 10. Once the arc 34 has been established to the workpiece 22, aportion of the tubular welding wire 50 (e.g., filler metals and alloyingcomponents) may be transferred (block 68) into the weld pool on thesurface of the workpiece 22 to form a weld bead of a weld deposit.Meanwhile, the remainder of the components of the tubular welding wire50 may be released (block 70) from the tubular welding wire 50 to serveas arc stabilizers, slag formers, and/or deoxidizers to control theelectrical characteristics of the arc and the resulting chemical andmechanical properties of the weld deposit.

By specific example, it is believed that, for certain embodiments, theGroup I or Group II metals (e.g., potassium and sodium ions) of theorganic stabilizer may generally separate from the organic stabilizerand provide a stabilization effect to the arc. Meanwhile, it is believedthat the organic portion (e.g., comprising at least carbon and hydrogen,but possibly including oxygen) may decompose under the conditions of thearc to provide a reducing (e.g., rich in hydrogen) atmosphere at or nearthe welding site. Accordingly, while not desiring to be bound by theory,it is believed that the resulting reducing atmosphere, and in potentialcombination with the Group I/Group II stabilizing metals, the rare earthcomponents, cyclical motion, and so forth, presently disclosed, providesa welding solution enabling high travel speeds and low-porosity, evenwhen welding coated workpieces or performing gap fills. For example, incertain embodiments, the tubular welding wire 50 may generally enablethe welding of thinner workpieces as well as painted, galvanized,galvannealed, plated, aluminized, chromed, carburized, or other similarcoated workpieces. For example, certain embodiments of the presentlydisclosed tubular welding wire 50 may enable welding workpieces havingthicknesses less than 5 mm or less than 4 mm, or workpieces havingthicknesses of approximately 1.3 mm or 1.2 mm, while maintaining hightravel speed (e.g., in excess of 30 in/min) and low-porosity, even whenperforming gap fills (e.g., 1-3 mm gap fills).

Results for an example all-weld metal welding experiment using anembodiment of the disclosed tubular welding wire 50 according to theprocess 60 is set forth below in Table 1. It should be appreciated thatthe weld chemistry illustrated in Table 1 accounts for certaincomponents of the weld metal (e.g., approximately 3% of the total weldmetal) with the remaining percentage provided by iron. As shown in Table1, the Charpy-V-Notch values for the resulting weld is approximately 35ft. lbs. at approximately −30° C. and is approximately 24 ft. lbs atapproximately −40° C. In certain embodiments, the Charpy-V-Notch valuesof a weld formed using the disclosed tubular welding wire 50 maygenerally range between approximately 20 ft. lbs. and approximately 45ft. lbs. Additionally, for the experiment illustrated in Table 1, theresulting weld afforded an ultimate tensile strength (UTS) ofapproximately 116 kilopounds per square inch (kpsi) and a yield strength(YS) of approximately 105 kpsi (e.g., with 20% elongation). In certainembodiments, the weld formed using the disclosed tubular welding wire 50may have a UTS in the range between approximately 100 kpsi andapproximately 130 kpsi and/or a YS in the range between approximately 95kpsi and approximately 115 kpsi and/or an elongation of approximately10% to approximately 40%.

Furthermore, it may be appreciated that the present approach enableslow-porosity (e.g., a low surface porosity and/or low total porosity)welds to be attained at high travel speed (e.g., in excess of 30 in/minor 40 in/min), even when welding coated workpieces. In certainembodiments, the low-porosity enabled by the presently disclosed tubularwelding wire 50 may provide a weld that is substantially non-porous. Inother embodiments, the disclosed tubular welding wire 50 may provide alow-porosity weld having only small voids or pores (e.g., less thanapproximately 1.6 mm in diameter) that are separated from one another bya distance greater than or equal to the respective diameter of eachpore. Further, in certain embodiments, the porosity may be representedas a sum of the diameters of the pores encountered per distance of theweld in a direction (e.g., along the weld axis). For such embodiments,the weld may have a porosity less than approximately 0.3 inches per inchof weld, less than approximately 0.25 inches per inch of weld, less thanapproximately 0.2 inches per inch of weld, or less than approximately0.1 inches per inch of weld. It may be appreciated that the porosity ofthe weld may be measured using an X-ray analysis, microscope analysis,or another suitable method.

TABLE 1 Welding experiment using an embodiment of tubular welding wire50. Welding Parameters Weld Chemistry (%) Amps 270 Carbon 0.126 Volts 28 Manganese 1.671 Current DCEN Phosphorus 0.009 Wire Feed Speed 425in/min Sulfur 0.012 Travel Speed  10 in/min Silicon 0.883 Charpy-V-Notchat −29° C.  35 ft. lbs. Copper 0.039 Charpy-V-Notch at −40° C.  24 ft.lbs. Chromium 0.045 Tensile Strength (UTS) 116 kpsi Vanadium 0.005Tensile Strength (YS) 105 kpsi Nickel 0.017 Molybdenum 0.006 Aluminum0.014 Titanium 0.033 Niobium 0.002 Cobalt 0.003 Boron 0.0008 Tungsten0.006 Tin 0.003 Zirconium 0.001 Antimony 0.002 Arsenic 0.003

FIG. 4 illustrates an embodiment of a process 80 by which the tubularwelding wire 50 may be manufactured. It may be appreciated that theprocess 80 merely provides an example of manufacturing a tubular weldingwire 50; however, in other embodiments, other methods of manufacturingmay be used to produce the tubular welding wire 50 without spoiling theeffect of the present approach. That is, for example, in certainembodiments, the tubular welding wire 50 may be formed via aroll-forming method or via packing the core composition into a hollowmetallic sheath. The process 80 illustrated in FIG. 4 begins with a flatmetal strip being fed (block 82) through a number of dies that shape thestrip into a partially circular metal sheath 52 (e.g., producing asemicircle or trough). After the metal strip has been at least partiallyshaped into the metal sheath 52, it may be filled (block 84) with thefiller (e.g., the granular core 54). That is, the partially shaped metalsheath 52 may be filled with various powdered alloying, arc stabilizing,slag forming, deoxidizing, and/or filling components. For example, amongthe various fluxing and alloying components, one or more organicstabilizer components (e.g., sodium carboxymethyl cellulose), one ormore carbon components (e.g., graphite powder), and one or more rareearth components (e.g., rare earth silicide) may be added to the metalsheath 52. Furthermore, in certain embodiments, other components (e.g.,rare earth silicide, magnetite, titanate, pyrite, iron powders, and/orother similar components) may also be added to the partially shapedmetal sheath 52.

Next in the illustrated process 80, once the components of the granularcore material 54 have been added to the partially shaped metal sheath52, the partially shaped metal sheath 52 may then be fed through (block86) one or more devices (e.g., drawing dies or other suitable closingdevices) that may generally close the metal sheath 52 such that itsubstantially surrounds the granular core material 54 (e.g., forming aseam 58). Additionally, the closed metal sheath 52 may subsequently befed through (block 88) a number of devices (e.g., drawing dies or othersuitable devices) to reduce the circumference of the tubular weldingwire 50 by compressing the granular core material 54. In certainembodiments, the tubular welding wire 50 may subsequently be heated tobetween approximately 300° F. and approximately 650° F. forapproximately 4 to 6 hours prior to packaging the tubular welding wireonto a spool, reel, or drum for transport, while, in other embodiments,the tubular welding wire 50 may be packaged without this baking step.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

The invention claimed is:
 1. A metal-cored welding wire, comprising: ametallic sheath disposed around a granular core, wherein the granularcore comprises a derivatized cellulose-based arc stabilizer component,wherein the derivatized cellulose-based arc stabilizer component is acellulose polymer that includes Group I metal ions selected from thegroup consisting of lithium (Li), sodium (Na), rubidium (Rb), and cesium(Cs), or includes Group II metal ions selected from the group consistingof beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), andbarium (Ba), or a combination thereof, that are chemically bound to thecellulose polymer, wherein the metal-cored welding wire comprisesbetween approximately 0.01% and approximately 5% derivatizedcellulose-based stabilizer component by weight, and wherein thederivatized cellulose-based arc stabilizer component decomposes underthe conditions of the arc and releases hydrogen and releases the Group Imetal ions, or the Group II metal ions, or the combination thereof, neara surface of a workpiece during arc welding.
 2. The metal-cored weldingwire of claim 1, wherein the derivatized cellulose-based arc stabilizercomponent comprises less than approximately 10% of the granular core byweight.
 3. The metal-cored welding wire of claim 1, wherein thederivatized cellulose-based arc stabilizer component comprises betweenapproximately 0.1% and approximately 1% of the metal-cored welding wireby weight.
 4. The metal-cored welding wire of claim 1, wherein thederivatized cellulose-based arc stabilizer component comprises: lithiumcarboxymethyl cellulose, sodium carboxymethyl cellulose, rubidiumcarboxymethyl cellulose, cesium carboxymethyl cellulose, magnesiumcarboxymethyl cellulose, calcium carboxymethyl cellulose, strontiumcarboxymethyl cellulose, or barium carboxymethyl cellulose, or acombination thereof.
 5. The metal-cored welding wire of claim 1, whereinthe granular core comprises a rare earth component comprising cerium,lanthanum, or a combination thereof, and wherein the rare earthcomponent comprises less than approximately 10% of the granular core byweight or comprises less than approximately 5% of the metal-coredwelding wire by weight.
 6. The metal-cored welding wire of claim 5,wherein the rare earth component comprises between approximately 0.5%and approximately 5% of the granular core by weight or comprises betweenapproximately 0.01% and approximately 2.5% of the metal-cored weldingwire by weight.
 7. The metal-cored welding wire of claim 1, wherein thegranular core comprises a carbon component comprising graphite,graphene, carbon black, lamp black, carbon nanotubes, diamond, or acombination thereof, and wherein the carbon component comprises lessthan approximately 10% of the granular core by weight or comprises lessthan approximately 5% of the metal-cored welding wire by weight.
 8. Themetal-cored welding wire of claim 7, wherein the carbon componentcomprises between approximately 0.01% and approximately 5% of thegranular core by weight or comprises between approximately 0.01% andapproximately 2.5% of the metal-cored welding wire by weight.
 9. Themetal-cored welding wire of claim 1, wherein the granular core comprisesan agglomerate comprising oxides of each of: one or more Group I orGroup II metals, titanium, and manganese; and wherein the agglomeratecomprises less than approximately 10% of the granular core by weight orcomprises less than approximately 5% of the metal-cored welding wire byweight.
 10. The metal-cored welding wire of claim 1, wherein thegranular core comprises between approximately 7% and approximately 40%of the metal-cored welding wire by weight, and wherein the derivatizedcellulose-based stabilizer component comprises less than approximately10% of the granular core by weight.
 11. The metal-cored welding wire ofclaim 1, wherein the derivatized cellulose-based stabilizer componentconsists essentially of: carbon, hydrogen, oxygen, and at least one of:the Group I metal ions and Group II metal ions.
 12. The metal-coredwelding wire of claim 1, wherein the derivatized cellulose-basedstabilizer component has a degree of substitution between approximately0.5 and approximately 2.5.
 13. A metal-cored welding wire, comprising: ametallic sheath and a granular core disposed within the metallic sheath,wherein the granular core comprises a derivatized cellulose-based arcstabilizer polymer that is a Group I salt of carboxymethyl cellulosethat includes chemically bound Group I metal ions selected from thegroup consisting of lithium (Li), sodium (Na), rubidium (Rb), and cesium(Cs), wherein the metal-cored welding wire comprises betweenapproximately 0.01% and approximately 5% derivatized cellulose-basedstabilizer polymer by weight, and wherein the derivatizedcellulose-based arc stabilizer polymer decomposes under the conditionsof the arc and releases both hydrogen and the Group I metal ions near asurface of a workpiece during arc welding.
 14. The metal-cored weldingwire of claim 13, wherein the derivatized cellulose-based arc stabilizerpolymer has a degree of substitution between approximately 0.5 andapproximately 2.5.
 15. The metal-cored welding wire of claim 13, whereinthe derivatized cellulose-based arc stabilizer polymer comprises lessthan approximately 10% of the granular core by weight.
 16. A metal-coredwelding wire, comprising: a metallic sheath and a granular core disposedwithin the metallic sheath, wherein the granular core comprises aderivatized cellulose-based arc stabilizer polymer that is a Group IIsalt of carboxymethyl cellulose that includes chemically bound Group IImetal ions selected from the group consisting of beryllium (Be),magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba), whereinthe derivatized cellulose-based arc stabilizer polymer decomposes underthe conditions of the arc and releases both hydrogen and the Group IImetal ions near a surface of a workpiece during arc welding.
 17. Themetal-cored welding wire of claim 16, wherein the derivatizedcellulose-based arc stabilizer polymer has a degree of substitutionbetween approximately 0.5 and approximately 2.5.
 18. The metal-coredwelding wire of claim 16, wherein the derivatized cellulose-based arcstabilizer polymer comprises less than approximately 10% of the granularcore by weight.